Method for sliding a seal with a lip onto a shaft, method for uncurling the lip, and apparatus for sliding the seal thereonto

ABSTRACT

When a seal ( 10 ) with a lip ( 10 A) is slid onto a shaft ( 14 ), the seal ( 10 ) is first slid from a D-cut portion ( 14 C) to the end of a shaft body ( 14 B) contiguous to the D-cut portion ( 14 C), and then is slid at a first speed (at 40 mm/s) from this end to a position in which the seal ( 10 ) does not come into contact with a large-diameter portion ( 14 A) of the shaft ( 14 ). Since there is a strong possibility that the lip ( 10 A) of the seal ( 10 ) will have been completely curled at this time. the seal ( 10 ) is pulled out at a second speed (at 10 mm/s) on the shaft body ( 14 B) from this position toward the D-cut portion ( 14 C), and the seal ( 10 ) is again slid inward at a third speed (at 70 mm/s) from this position to an appropriate position. Thus, the seal ( 10 ) is slid without the lip ( 10 A) being curled. The sliding operations at the second and third speeds may be performed a plurality of times. Another way of sliding the seal ( 10 ) without the lip ( 10 A) being curled is to slide the seal ( 10 ) onto the shaft ( 14 ) while rotating the shaft ( 14 ) and the seal ( 10 ) relatively with each other. Additionally, if the shaft ( 14 ) and the seal ( 10 ) are rotated relatively with each other while positioning the seal ( 10 ) at the D-cut portion ( 14 C), the lip ( 10 A) can be uncurled.

This application is a division of U.S. application Ser. No. 08/991,861,filed Dec. 16, 1997.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method for sliding a seal with a lip, suchas an oil seal or G seal, onto a shaft, a method for recovering the curlof the lip occurring when the seal is slid onto the shaft, and anapparatus for sliding the seal onto the shaft.

2. Description of the Related Art

Conventionally, a seal with a funnel-shaped lip is known. The lipprojects toward the inner circumference of an annular body of the seal.In this seal, the end of the lip which is formed of an elastic member,such as rubber, is in direct contact with a shaft, so that the content(oil or ponder) inside the seal can be prevented from leaking outsideand, at the same time, foreign objects (dust or the like) can beprevented from invading inside of the seal from the outside.

When the seal is slid onto the cylindrical shaft, which is acorresponding part to be incorporated with the seal, in a state in whichthe front end of the lip is directed toward the shaft, there is a casein which the lip is turned inward or is curled inside of the seal. Thiscase makes it impossible to prevent the leakage of the content to theoutside and prevent the invasion of the foreign objects through theseal.

For this reason, an apparatus has been proposed for sliding a seal witha lip onto a shaft without inverting or curling the lip in such a waythat a pipe-like member is inserted in the seal in advance and, in thisstate, the seal is slid onto the shaft and there after the pipe-likemember is pulled away from the seal (see Japanese Utility ModelApplication Early Laid-Open Publication No. Hei 4-76331, for example).Also, a seal with a lip has been proposed which is provided with aspring for pressing the seal so as not to curl the lip when sliding theseal onto a shaft (see Japanese Utility Model Application EarlyLaid-Open Publication No. Hei 6-30565, for example).

There is also a method for detecting whether a lip of a seal has beencurled. For example, in Japanese Registered Utility Model No. 3007446, amethod is proposed which includes the steps of forming a notch in thecircumferential edge of a seal with a lip and making an air-leakage testin order to easily detect whether the lip of the seal has been curled.

In the aforementioned apparatus disclosed by Japanese Utility ModelApplication Early Laid-Open Publication No. Hei 4-76331, a mechanism forinserting the pipe-like member into the seal is also required inaddition to a mechanism for sliding the seal onto the shaft. Therefore,disadvantageously, the apparatus requires a larger space, and aninserting operation must be carried out twice. As a result, thestructure of the apparatus becomes complicated. In the aforementionedseal disclosed by Japanese Utility Model Application Early Laid-OpenPublication No. Hei 6-30565, the seal is provided with an annularportion to which a garter sprint is attached to prevent the lip fromcurling. This makes the structure of the seal unique and complicated.

In the aforementioned method disclosed by Japanese Registered UtilityModel No. 3007446, a device for supplying air is inevitably required tomake the air-leakage test. As a result, large-sized assembly equipmentis required, and thus equipment costs are raised.

Further, the prior art methods and apparatus mentioned above are eachproposed from only the viewpoint of sliding the seal onto the shaft sothat the lip is not turned inward or is not curled. In other words, themethods and apparatus pay no attention to uncurling the lip which hasbeen curled.

SUMMARY OF THE INVENTION

It is a first object of this invention to provide a method for preciselysliding a seal onto a shaft without using a large apparatus space forthe seal sliding, a peculiar structure of the seal, and an air-leakingtest or the like, and an apparatus for sliding the seal by theseal-sliding method.

It is a second object of this invention to provide a method for easilyreturning a curled seal lip into the initial state in the case where alip is curled when a seal is slid, and an apparatus for sliding the sealby the curled-seal-lip-returning method.

In order to achieve the first object, the seal-sliding method accordingto this invention comprises the step of sliding a seal while the shaftis rotated around the axial line of a shaft when the seal with a lip isslid onto the shaft (according to an aspect of this invention). Further,the apparatus for realizing the step of the seal-sliding methodaccording to this invention, that is, the seal-sliding apparatus forsliding the seal with the lip onto the shaft, comprises a holding meansfor holding releasably the seal in the direction of the axial line ofthe shaft, and a shaft-rotating means for rotating the shaft, whereinthe seal is slid onto the shaft while the shaft is rotated around theaxial line by the shaft-rotating means (according to another aspect ofthis invention).

According to one of the two aspects mentioned above of this invention,since the shaft and the lip make friction in a rotational direction witheach other when the shaft is rotated, the frictional resistance of theseal-sliding direction becomes lower, so that the lip can be preventedfrom being curled by the frictional force of the seal-sliding direction.

Further, in order to attain the first object, the seal-sliding methodaccording to this invention comprises the step of sliding a seal whilethe seal is rotated around the axial line of a shaft when the seal witha lip is slid onto the shaft (according to another aspect of thisinvention). Further, the apparatus for realizing the step of theseal-sliding method according to this invention, that is, theseal-sliding apparatus for sliding the seal with the lip onto the shaft,comprises a holding means for holding releasably the seal in thedirection of the axial line of the shaft, and a seal-rotating means forrotating the seal which is held by the holding means, wherein the sealis slid onto the shaft while the seal is rotated around the axial lineof the shaft by the seal-rotating means (according to another aspect ofthis invention).

According to one of the two aspects mentioned above of this invention,since the shaft and the lip make friction in a rotational direction witheach other when the seal is rotated, the same function as the functionobtained when the shaft is rotated can be obtained. Further, theconstruction according to one of these two aspects is more effective inthe case where the shaft cannot be rotated.

Further, in order to attain the first object, the seal-sliding methodaccording to this invention comprises the step of sliding a seal while ashaft and the seal are rotated together around the axial line of theshaft when the seal with a lip is slid onto the shaft (according toanother aspect of this invention). Further, the apparatus for realizingthe step of the seal-sliding method according to this invention, thatis, the seal-sliding apparatus for sliding the seal with the lip ontothe shaft, comprises a holding means for holding releasably the seal inthe direction of the axial line of the shaft, a seal-rotating means forrotating the seal which is held by the holding means, and ashaft-rotating means for rotating the shaft, wherein the seal is rotatedby the seal-rotating means and the seal is slid onto the shaft while theshaft is rotated by the shaft-rotating means (according to anotheraspect of this invention).

According to one of the two aspects mentioned above of this invention,since the shaft and the lip make friction in a rotational direction witheach other when the seal and the shaft are rotated. The same function asthe function obtained when either the shaft or the seal is rotated canbe obtained.

Further, in order to attain the first object, the seal-sliding methodaccording to this invention comprises the steps of making a firstoperation in which a seal with a lip is at first slid onto a shaft, thenmaking a second operation in which the seal is slid back to a positionwhere the seal cannot be slid away from the shaft after the firstoperation, and making a third operation once or many times in which theseal is slid again onto the shaft after the third operation (accordingto another aspect of this invention). Further, the apparatus forrealizing the steps of the seal-sliding method according to thisinvention, that is, the seal-sliding apparatus for sliding the seal withthe lip onto the shaft, comprises a holding means for sliding andholding the seal onto the shaft, and a controlling means for controllingthe holding means so that the first operation in which the seal is atfirst slid onto the shaft is made, then the second operation in whichthe seal is slid back to the position where the seal cannot be slid awayfrom the shaft after the first operation is made, and the thirdoperation in which the seal is slid again onto the shaft after thesecond operation is made once or many times (according to another aspectof this invention).

According to one of the two aspects mentioned above of this invention,following, the first operation of sliding the seal, the second operationof sliding the seal back is made, so that the seal which has been curledin the first operation can be returned into the initial state by thefrictional force caused in the second operation where the seal lip makesfriction with the shaft. Then, the seal in the initial state is slidagain in the third operation, so that the seal can be slid onto theshaft so that the lip is not curled.

Next, in order to attain the second object, the curled-lip-recoveringmethod, that is, a method for returning a lip which has been curled intothe initial state when a seal with the lip is slid onto a shaftaccording to this invention comprises the steps of cutting in advance apart of the outer circumferential surface of the shaft to form a cutportion, positioning the seal in the cut portion when the seal is slidand at least a part of the lip is curled, and rotating the shaftrelatively to the seal to returning the curled lip into the initialstate (according to another aspect of this invention). Further, theapparatus for realizing the steps of the curled-lip-recovering methodaccording to this invention, that is, the seal-sliding apparatus forsliding the seal with the lip onto the shaft, comprises a first meansfor curling at least the part of the lip when the seal is slid, a secondmeans for positioning the seal in the cut portion formed in the outercircumferential surface of the shaft and rotating the shaft relativelyto the seal to returning the lip which has been curled by the firstmeans into the initial state, and a third means for keeping the sealwhose lip has been brought into the initial state in a predeterminedposition (according to another aspect of this invention).

According to one of the two aspects mentioned above of this invention ifonly the shaft would be rotated relatively to the seal when the seal isslid onto the shaft and the lip is curled, the curled lip can be easilyreturned into the initial state. As a result, the seal whose lip hasbeen brought into the initial state can be slid in the predeterminedposition of the shaft as it is.

Further, in order to attain the second object, the curled-lip-recoveringmethod, that is, a method for returning a lip which has been curled intothe initial state when a seal with the lip is slid onto a shaftaccording to this invention comprises the step of positioning the sealin a circumferential groove formed in the outer surface of the shaft sothat the curled lip is returned into the initial state (according toanother aspect of this invention). Further, the apparatus for realizingthe steps of the curled-lip-recovering method according to thisinvention, that is, the seal-sliding apparatus for sliding the seal withthe lip onto the shaft, comprises a curled-lip-recovering means forpositioning the seal in the circumferential groove formed in the outersurface of the shaft and returning the curled lip into the initial state(according to another aspect of this invention).

According to one of the two aspects mentioned above of this invention,if only the seal would be positioned in the circumferential groove, thecurled lip can be returned into the initial state by the recoveringforce of the lip. In the case where the curled lip is returned into theinitial state even though the seal is positioned in the circumferentialgroove, when the shaft is rotated relatively to the seal in a statewhere the seal is positioned in the circumferential groove, the curledlip can be returned into the initial state without any failure.

Further, in order to attain the second object, the curled-lip-recoveringmethod, that is, a method for returning a lip of a seal which has beencurled into the initial state when the seal with the lip is slid onto ashaft according to this invention comprises the steps of connecting ajig member having a cut portion into which a part of the outercircumferential surface has been cut and the shaft on the central axisof the shaft, rotating the jig member relatively to the seal when theseal is positioned in the cut portion, and returning the curled lip intothe initial state (according to another aspect of this invention).Further, the apparatus for realizing the steps of thecurled-lip-recovering method according to this invention, that is, theseal-sliding apparatus for sliding the seal with the lip onto the shaft,comprises a curled-lip-recovering means for connecting the jig memberhaving the cut portion into which the part of the outer circumferentialsurface has been cut to the shaft on the central axis, rotating the jigmember relatively to the seal when the seal is positioned in the cutportion, and returning the curled lip into the initial state (accordingto another aspect of this invention).

According to one of the two aspects mentioned above of this invention,the curled lip can be returned into the initial state with the cutportion formed in the jig member, which is effective in the case wherethe cut portion cannot be formed in the shaft.

Further, in order to attain the second object, the curled-lip-recoveringmethod, that is, a method for returning a lip of a seal which has beencurled into the initial state when the seal with the lip is slid onto ashaft according to this invention comprises the steps of connecting ajig member having a circumferential groove in the outer circumferentialsurface and the shaft on the central axis of the shaft, positioning theseal at the cut portion, and returning the curled lip into the initialstate (according to another aspect of this invention). Further, theapparatus for realizing the steps of the curled-lip-recovering methodaccording to this invention, that is, the seal-sliding apparatus forsliding the seal with the lip onto the shaft, comprises acurled-lip-recovering means for connecting the jig member having acircumferential groove in the outer circumferential surface and theshaft on the central axis of the shaft, positioning the seal in thecircumferential groove, and returning the curled lip into the initialstate (according to another aspect of this invention).

According to one of the two aspects mentioned above of this invention,the curled lip can be returned into the initial state with thecircumferential groove formed in the jig member, which is effective inthe case where the circumferential groove cannot be formed in the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of an apparatus for sliding aseal onto a shaft while the shaft is rotated.

FIG. 2 is a schematic perspective view of another example of a mechanismfor transmitting the rotating force.

FIG. 3 is a schematic perspective view of a seal-sliding apparatus forsliding a seal onto a shaft while the seal is rotated.

FIG. 4 is a schematic perspective view of a seal-sliding apparatus forsliding a seal onto a shaft while both of the seal and the shaft arerotated.

FIG. 5 is a plan view of a robot for sliding a seal.

FIG. 6 is a side view of the robot shown in FIG. 5.

FIG. 7 is a plan view of a chuck hand.

FIG. 8 is a side view of the chuck hand shown in FIG. 7.

FIG. 9 is a plan view of another chuck hand.

FIG. 10 is a side view of the chuck hand shown in FIG. 9.

FIG. 11 is a plan view of another chuck hand.

FIG. 12 is a side view of the chuck hand shown in FIG. 11.

FIG. 13 is an enlarged perspective view of the shaft onto which the sealis slid.

FIG. 14 is a sectional view of the seal which has been slid in a normalcondition on the shaft.

FIG. 15 is a sectional view of the seal which has not been slid in anormal condition on the shaft.

FIG. 16 is an explanatory drawing showing an operation in which the sealis slid.

FIG. 17 is an explanatory diagram showing a first method for judgingthat the lip is curled.

FIG. 18 is an explanatory diagram showing a second method for judgingthat the lip is curled.

FIG. 19 is an explanatory diagram showing a third method for judgingthat the lip is curled.

FIG. 20 is an explanatory diagram showing a fourth method for judgingthat the lip is curled.

FIG. 21 is a flow chart showing a fifth method for judging that the lipis curled.

FIG. 22 is a schematic view of the seal and the shaft, showing a methodfor returning the curled lip into the initial state with a D-cut portionformed in the end of the shaft.

FIG. 23(A) is a front view of a shaft with the D-cut portion.

FIG. 23(B) is a sectional view of the shaft, cut along a B—B line inFIG. 23(A).

FIG. 24(A) is a front view of a shaft with a cylindrical convex cutsurface.

FIG. 24(B) is a sectional view of the essential part of the shaft inFIG. 24(A).

FIG. 25(A) is a front view of a shaft with a cylindrical concave cutsurface.

FIG. 25(B) is a sectional view of the essential part of the shaft inFIG. 25(A).

FIG. 26(A) is a front view of a shaft with a groove-like cut surface.

FIG. 26(B) is a sectional view of the essential part of the shaft inFIG. 26(A).

FIG. 27(A) is a front view of a shaft with a flat cut surface on bothside of the shaft.

FIG. 27(B) is a sectional view of the essential part of the shaft inFIG. 27(A).

FIG. 28(A) is a front view of a shaft with a cylindrical convex cutsurface on both side of the shaft.

FIG. 28(B) is a sectional view of the essential part of the shaft inFIG. 28(A).

FIG. 29 is a schematic view of the seal and the shaft, showing a methodfor returning the curled lip into the initial state with a D-cut portionformed in the middle part in the longitudinal direction of the shaft.

FIG. 30 is a schematic view of the seal and the shaft, showing a methodfor returning the curled lip into the initial state with acircumferential groove formed in the outer surface of the shaft.

FIG. 31 is a schematic view of the seal and the shaft, showing a methodfor returning the curled lip into the initial state with a jig memberhaving a D-cut portion.

FIG. 32 is a schematic view of the seal and the shaft, showing therelation between the D-cut portion of the jig member and the innerdiameter of the lip.

FIG. 33(A) is a perspective view of a jig member having a square-pillarportion and a shaft having a square-pillar-shaped hole, showing a methodfor connecting the jig member with the shaft.

FIG. 33(B) is a perspective view of a jig member having a cylindricalportion and a shaft having a cylindrical hole, showing a method forconnecting the jig member with the shaft.

FIG. 33(C) is a perspective view of a jig member having a cylindricalportion and a magnet portion and a shaft having a cylindrical hole,showing a method for connecting the jig member with the shaft.

FIG. 33(D) is a perspective view of a jig member having a magnet portionand a shaft, showing a method for connecting the jig member with theshaft.

FIG. 34(A) is a front view of a jig member having a cylindrical convexcut surface.

FIG. 34(B) is a sectional view of the essential part of the jig memberin FIG. 34(A).

FIG. 35(A) is a front view of a jig member having a cylindrical concavecut surface.

FIG. 35(B) is a sectional view of the essential part of the jig memberin FIG. 35(A).

FIG. 36(A) is a front view of a jig member having a groove-like cutsurface.

FIG. 36(B) is a sectional view of the essential part of the jig memberin FIG. 36(A).

FIG. 37(A) is a front view of a jig member having a flat cut surface onboth side of the jig member.

FIG. 37(B) is a sectional view of the essential part of the jig memberin FIG. 37(A).

FIG. 38(A) is a front view of a jig member having a cylindrical convexcut surface on both side of the jig member.

FIG. 38(B) is a sectional view of the essential part of the jig memberin FIG. 38(A).

FIG. 39 is a front view of a jig member having an inclined surface in astepped portion.

FIG. 40 is a schematic view of the seal and the shaft, showing a methodfor returning the curled lip into the initial state with a jig memberhaving a circumferential groove.

DETAILED DESCRIPTION OF THE EMBODIMENT

An embodiment of the present invention will be hereinafter describedwith reference to the accompanying drawings.

FIG. 1 is a schematic perspective view of an apparatus for sliding aseal. In FIG. 1, reference character 10 designates a seal with a lip,which is held by a holding member 11. The holding member 11 is held by achuck hand 12, and the seal 10 is held indirectly by the chuck hand 12.Naturally, the seal 10 may also be held directly by the chuck hand 12without the holding member 11 therebetween.

The chuck hand 12 is attached to a robot 13 and can make aforward-and-backward motion in the directions of X, Y, and Z shown inFIG. 1. The robot 13 comprises a first member 13A disposed in theX-direction, a second member 13B disposed in the Y-direction, and athird member 13C disposed in the Z-direction. Each of the second member13B, the third member 13C, and the chuck hand 12 makes aforward-and-backward motion in the X-direction along the first member13A, in the Y-direction along the second member 13B, and in theZ-direction along the third member 13C, respectively. Herein, accordingto this embodiment, the robot having three axes is shown as an example,however, a robot having an axis or two axes may also be used. Further,instead of the type of perpendicular lines, a robot in a scalar type orpolar-coordinate type may also be used.

In FIG. 1, reference character 14 designates a shaft on which the seal10 is slid, and the shaft 14 is attached to both end surfaces of acolumnar or cylindrical member 15. This member 15 is disposed rotatableon an operational stand 16, and a turnable plate 17 is disposed abovethe member 15. One end of the turnable plate 17 is connected to a firstcylinder 18, and the first cylinder 18 is held on a second cylinder 19The turnable plate 17, the first cylinder 18, and the second cylinder 19are mechanisms for transmitting the rotational force to the member 15.

In the seal-sliding apparatus, when the seal 10 is slid onto the shaft14, the holding member 11 is held by and between the chuck hand 12, andthe first cylinder 18 is pulled down by the second cylinder 19. Thefirst cylinder 18 is pulled down, so that the turnable plate 17 can bepressed onto a part of the outer circumferential surface of the member15. Thereafter, when the first cylinder 18 allows the turnable plate 17to make a forward-and-backward motion in the Y-direction, the member 15repeats a right or reversal rotational motion together with the shaft14. Then, the chuck hand 12 is moved in the Y- or Z-direction by thedrive of the robot 13, the center of the seal 10 held on the holdingmember 11 corresponds to the central axis of the shaft 14, the chuckhand 12 is moved in the X-direction, the seal 10 comes close to theaxial end of the shaft 14. and thus the seal 10 is slid onto the shaft14 which is making the right or reversal rotational motion.

At this time, the shaft 14 makes a frictional rotation with the lip ofthe seal 10, so that the friction in the seal-sliding direction can bemade smaller. Further, the distance at which the chuck hand 12 is movedin the X-direction is regulated, so that the seal 10 which is slid ontothe shaft 14 can be brought to a predetermined position.

FIG. 2 is a schematic perspective views of another mechanism fortransmitting the rotating force. In this example, a rotating roller 20and a rotated roller 21 are disposed above and in parallel with themember 15. The rotating roller 20 and the rotated roller 21 are disposedrotatably inside of a holding body 22, and a part of the circumferentialsurface of the rotating roller 20 and one of the rotated roller 21 arein contact with each other. When a motor 23 which is attached to theholding body 22 and is connected to the rotating roller 20 is rotated,the rotating roller 20 and the rotated roller 21 are rotated in thereversal directions for each other. A cylinder 24 is connected to theholding body 22.

When the seal 10 is slid onto the shaft 14, the holding body 22 ispressed downward with the cylinder 24, the rotating roller 20 is pressedonto the outer circumferential surface of the member 15, the revolvingforce of the motor 23 is transmitted to the member 15 via the rotatingroller 20, and the member 15 is rotated together with the shaft 14. Inthe case where the member 15 is reversely rotated, the holding body 22is moved in the A-direction with a cylinder (not shown), and the rotatedroller 21 comes into contact with the outer circumferential surface ofthe member 15. Herein, when either the rotating roller 20 or the rotatedroller 21 is used, the shaft 14 can be continuously rotated in onedirection.

In the rotating-force-transmitting mechanism shown in FIG. 2, the outercircumferential surface of the rotating roller 90 and that of therotated roller 21 are in contact with each other and are rotated in thereversal directions for each other. However, a space may be left betweenthe rotating roller 20 and the rotated roller 21 so that only therotating roller 20 is rotated by the revolving force of the motor 23.According to this construction, when the holding body 22 is presseddownward, both of the rotating roller 20 and the rotated roller 21simultaneously come into contact with the outer circumferential surfaceof the member 15, so that the rotating roller 20, the rotated roller 21,and the member 15 can be rotated in a stable state. Herein, in thiscase, if the motor 23 is reversely revolved, the member 15 is reverselyrotated.

Although the mechanisms shown in FIGS. 1 and 2 are constructed so thatthe member is rotated, there can also be considered a mechanism which isconstructed so that the member is not rotated. Such a mechanism isconstructed so that the seal is rotated. FIG. 3 shows this example. InFIG. 3, the chuck hand 12 is connected to the robot 13 via a rotatingmechanism 25. The rotating mechanism 25 can be rotated in one directionand in the reversal direction, and the chuck hand 12 is also rotated inthe right or reversal direction according to the right and reversalrotations. Herein, a member 26 mounted on the operational stand 16 has,for example, a square-pillar shape, so that it cannot be rotated. Theshaft 14 is attached to the member 26.

When the seal 10 held on the holding, member 11 is slid onto the shaft14, the robot 13 allows the center of the seal 10 to correspond to thecentral axis of the shaft 14 and sequently, the rotating mechanism 25allows the seal 10 to rotate in the right or reversal direction so thatthe seal 10 is slid onto the shaft 14. At this time, in the same way asshown in FIG. 1 or 2, the shaft 14 makes a frictional rotation with thelip of the seal 10, so that the friction in the seal-sliding directioncan be made smaller. Herein, a rotating mechanism be a motor or a rotarycylinder is desired to be used as the rotating mechanism 25.

FIG. 4 shows an example of sliding a seal onto a shaft while both of amember and the shaft are rotated. In the example shown in FIG. 4, in thecase where a member 27 mounted on the operational stand 16 is notdirectly rotated, both of the seal 10 and the member 27 are rotated. Inthe same way as shown in FIG. 3, the chuck hand 12 is connected to therobot 13 via the rotating mechanism 25. The member 27 is held by andbetween a chuck hand 28, and the chuck hand 28 is fixed on theoperational stand 16 via a rotating mechanism 29. The shaft 14 isattached to the member 27.

When the seal 10 is slid onto the shaft 14, the member 27 is rotated bythe drive of the rotating mechanism 29, as well as the chuck hand 12 isrotated by the drive of the rotating mechanism 25. In brief, the seal 10is slid onto the shaft 14 while the seal 10 and the shaft 14 are eachrotating. At this time, the shaft 14 makes a frictional rotation withthe lip of the seal 10, so that the friction in the seal-slidingdirection can be made smaller. Herein, a rotating mechanism by a motoror a rotary cylinder is desired to be used as the rotating mechanism 29.In addition, it is preferable that the directions in which the rotatingmechanisms 25, 29 are rotated are reverse to each other.

Next, there will be explained the construction of the robot 13 indetail.

FIG. 5 is a plan view of the robot 13 and FIG. 6 is a side view of therobot 13. The robot 13 is mounted on an installment stand 30 and ispositioned on the operational stand 16 (see FIG. 1 or 3). The chuck hand12 includes a load cell 31. A detected signal (a detected load signal)in the load cell 31 is transmitted to a computer 33 via a load-cellamplifier 32. A robot controller 34 for controlling the operation of therobot 13 is disposed, and the robot controller 34 is connected to thecomputer 33 so that signals can be sent and received between the robotcontroller 34 and the computer 33.

FIG. 7 is a plan view of a chuck hand, showing its construction indetail, and FIG. 8 is a side view of the chuck hand. The chuck hand 12is connected to a portion to which the hand of the robot 13 is attachedvia a base 35. Herein, the base 35 shown in FIG. 7 is used so that thechuck hand 12 is slid upward and downward (in the Z-direction) along thehand-attached portion of the robot 13. If the rotating mechanism 25shown in FIGS. 3 and 4 is used in addition to the aforementionedconstruction, the chuck hand 12 can also be turned. According to thisconstruction, the aforementioned operation can also be made even in thecase where the direction in which the chuck hand 12 chucks the seal 10or the holding member 11 (hereinafter, the seal or the holding memberwill be referred to as a seal), that is, the direction in which the sealis supplied, is different from the direction in which the seal is slid.

A bracket 36 which is kept curled in an L-shape is fixed on the back end(the left side and the right side correspond to the back side and thefront side, respectively, in FIG. 7) of the base 35. A guide rail 35Bhaving stoppers 35A at both ends thereof is attached to the plane in thesubstantially middle part of the base 35, and a sliding portion 37 isdisposed slidably on the guide rail 35B. In short, the sliding portion37 can be moved along the guide rail 35B in the right and leftdirections in FIG. 7 (in the direction in which the seal is slid).

A moving base 38 is fixed on the sliding portion 37. A chuck 39 betweenwhich the seal is held is attached to the front end of the moving base38. A sensor 40 for detecting that the seal lies is attached to thechuck 39, and the seal-detecting sensor 40 can detect that the seal liesand inform the robot controller 34 of it.

A dog 41 for detecting a jam is attached to the back end of the movingbase 38. When the moving base 38 is moved toward a direction of beingaway from a work (in the left direction in FIG. 7), the jam-detectingdog 41 comes across a sensor 42 for detecting the jam which is fixed onthe bracket 36. The load cell 31 is fixed to the back end of the movingbase 38 via an attachment block 38A.

Two axes 43 having a flange-shaped end are attached to the end oppositeto the attachment block 38A of the load cell 31. Each axis 43 penetratesa hole formed in the bracket 36. A coil spring 44 is disposed betweenthe end of the load cell 31 and the bracket 36. The axis 43 penetratesthe coil spring 44, and a space is defined between the coil spring 44and the axis 43 so that the coil spring 44 does not come into contactwith the axis 43. While a seal-sliding operation is not made, thesliding portion 37 is pressed onto the stopper 35A closer to the chuck39 by the force of the coil spring 44.

FIG. 9 is a plan view of another chuck hand, and FIG. 10 is a side viewof the chuck hand shown in FIG. 9. In a chuck hand 12′ shown in FIGS. 9and 10, a mechanism 45 for correcting the difference in position betweenthe seal and the axis on which the seal is slid is disposed between themoving base 31 and the chuck 39. Although the correcting mechanism 45 isflexible in its radial direction, a plurality of members (three membersin FIG. 10) 46 which is inflexible in the direction along the axialcenter of the correcting mechanism 45 are disposed in parallel in thecorrecting mechanism 45, so that the entire chuck 39 can be moved onlyin the radial direction of the axis on which the seal is slid.

FIG. 11 is a plan view of another chuck hand, and FIG. 12 is a side viewof the chuck hand shown in FIG. 11. In a chuck hand 12″ shown in FIGS.11 and 12, instead of the jam-detecting dog 41, the jam-detecting sensor42, and the coil spring 44 in the aforementioned chuck hand 12′, a coilspring 47, an air cylinder 48, a shaft 49, and a sensor 50 are disposed.According to this example, only one axis is disposed as the axis 43.

The coil spring 47 is disposed between a flange portion of the axis 43and the bracket 36 so that it does not come into contact with the outercircumferential surface of the axis 43. The air cylinder 48 is fixed onthe bracket 36 in the position opposite to the load cell 31 for thebracket 36. The shaft 49 is attached to the air cylinder 48 and is incontact with an end of the load cell 31. The sensor 50 for detecting theposition of the shaft 49 is attached to the air cylinder 48. The sensor50 is connected to the robot controller 34, and thus the information ona hand jam can be sent to the robot controller 34. Herein, the force bywhich the air cylinder 48 presses out the shaft 49 is designed to belarger than the force of the sprint 47, so that the shaft 49 can bepositioned in a state where the air cylinder 48 has completely pressedthe shaft 49. Thereby, the chuck 39 and the like which is mounted on themoving base 38 can be positioned here.

In FIG. 12, reference character 51 designates an air compressor forsupplying air into the air cylinder 48, and 52 designates a regulatorfor regulating the amount in which air flows.

FIG. 13 is an enlarged perspective view of the shaft 14 onto which theseal is slid. Although not shown in FIGS. 1 to 4, the shaft 14 comprisesa cylindrical large-diameter portion 14A, an shaft body 14B projectingfrom the cylindrical large-diameter portion 14A, and a D-cut portion 14Cformed in the end part of the shaft body 14B.

FIG. 14 shows an example where the seal 10 having a lip 10A is kept slidon the shaft 14 in a desirable form (in a state where the lip 10A is notcurled), and FIG. 15 shows an example where the seal 10 is kept slid onthe shaft 14 in an undesirable form (in a state where the lip 10A iscurled). In the state shown in FIG. 14 where the seal 10 is kept slid onthe shaft 14, the lip 10A is not kept curled, so that oil or dust can beprevented from flowing from the large-diameter portion 14A to the D-cutportion 14C of the shaft 14. On the other hand, in the state shown inFIG. 15 where the lip 10A is curled, oil or dust may flow from thelarge-diameter portion 14A to the D-cut portion 14C.

Next, there will be explained an operation in which the seal 10 is slid.

FIG. 16 shows an example of the operation in which the seal 10 is slidonto the shaft 14 having the configuration shown in FIG. 13. Herein,naturally, the lip 10A is directed toward the shaft 14 when the seal 10is slid onto the shaft 14.

At first, the seal 10 is moved at an appropriate speed from a position 0to a position 2 in FIG. 16, and then the seal 10 is moved from the D-cutportion 14C of the shaft 14 and is slid onto the end of the cylindricalshaft body 14B thereof. Sequently, the seal 10 is moved at a first speed(for example, at 40 mm/s) from the position 2 to a position 3. Herein,the position 3 should be determined so that the seal 10 does not comeinto contact with the end surface of the large diameter portion 14A ofthe shaft 14. At this time, the lip 10A of the seal 10 is probablythought to be completely curled. Thereafter, the seal 10 is pulled at asecond speed (for example, at 10 mm/s) from the position 3 to a position4. Then, the seal 10 is slid again at a third speed (for example, at 70mm/s) from the position 4 to a position 5. The operations at the secondspeed and at the third speed of the aforementioned operations aredesired to be made once or a plurality of times (three times in FIG. 16)so that the seal 10 is in a predetermined position when the finalsliding operation has been made.

In general, among the aforementioned operations, in the pullingoperations which are made from the position 3 to the position 4, fromthe position 5 to a position 6, and from a position 7 to a position 8,the lip 10A which has been curled is recovered as well as the seal 10 ispulled toward the end of the shaft 14. The longer the distance at whichthe seal 10 is pulled and moved is, the easier it is that the curled lip10A is recovered. On the other hand, in the movements which are madefrom the position 2 to the position 3, from the position 4 to theposition 5, from the position 6 to the position 7, and from the position8 to a position 9, the seal 10 is slid inward on the shaft 14, which maycause the lip 10A to be curled. The shorter the distance at which theseal 10 is slid and moved inward is, the more the lip 10A is preventedfrom being curled.

In consideration of the two conditions mentioned above, in order toprevent the lip 10A from being curled, it is desirable that the slid-indistance is shorter and the pulled-out distance is longer, however, thetwo conditions cannot be met at one time because they are contrary toeach other. Therefore, as mentioned above, the difference between thespeed of the sliding-in operation and that of the pulling-out operationis made, in short, the speed of the sliding-in operation is made higherso as to prevent the lip 10A from being curled and that of thepulling-out operation is made lower so as to make the lip 10A moreeasily recovered.

In the case where the shaft onto which the seal 10 is slid has a stepportion such as the D-cut portion 14C of the shaft 14 shown in FIG. 16,since the lip 10A is curled in the step portion, as shown in the exampleof FIG. 16, the pulling-out operation is designed to be made in thecylindrical part (the part of the shaft body 14B) of the shaft 14.

When the relative rotation between the seal 10 and the shaft 14 is madein the sliding-in operation from the position 4 to the position 5, fromthe position 6 to the position 7, and from the position 8 to a position9, the frictional force between the lip 10A and the shaft 14 isgenerated not only in the sliding-in direction but also in therotational direction of the shaft 14. and thereby the frictional forcein the sliding-in direction is dispersed. As a result, the lip 10A canbe prevented from being curled in the sliding-in operation.

When the seal 10 comes into contact with the shaft 14 in theaforementioned normal operation, even though the seal 10 is shifted fromthe shaft 14 in the radial direction of the shaft 14, the correctingmechanism 45 shown in FIGS. 9 to 12 can correct the mutual positionalshift. On the other hand, the same function can be fulfilled in anunusual operation, that is, in a hand-jam operation. In the case wherethe chuck hand has the construction shown in FIGS. 7 to 10, when thechuck 39 is pressed by the large force, the spring 44 is contracted bythe moving base 38 via the load cell 31. When the chuck 39 is pressed bylarger force, the jam-detecting dog 41 comes across the jam-detectingsensor 42, then the information is sent to the robot controller 34, andthereby an emergency stop of the robot 13 is made.

In the case where the chuck hand 12 has the construction shown in FIGS.11 and 12, even though the chuck 39 is pressed by the force, any part ofthe seal 10 is not moved in the shaft-central direction unless the forceexceeds a limited strength. When the chuck 39 is pressed by largerforce, the shaft 49 of the air cylinder 48 is pressed and moved by themoving base 38 via the load cell 31. Then, when the shaft 49 reaches thesensor 50, the sensor 50 detects that there is the shaft 49, theinformation is sent to the robot controller 34, and thereby an emergencystop of the robot 13 is made.

Next, there will be explained a method for judging whether the lip 10Ais kept curled when the seal 10 has been slid onto the shaft 14. Herein,as the curled-lip judging method, there will be explained a curled-lipjudging method 1 shown in FIG. 17, a curled-lip judging method 2 shownin FIG. 18, a curled-lip judging method 3 shown in FIG. 19, and acurled-lip judging method 4 shown in FIG. 20.

[Curled-Lip Judging Method 1]

During the seal-sliding-in operation, the voltage proportionate to theload applied on the load cell 31 is outputted from the load cell 31, andthe voltage is amplified by the load-cell amplifier 32. The transitionof the wave of the load is shown in FIG. 17. The axis of ordinates, andthat of abscissas, in a graph shown in FIG. 17 show the sliding-in forceor the pulling-out force (Kgf), and time (seconds), respectively. Points0 to 9 shown in the wave transition graph correspond to the sliding-inforce or the pulling-out force in the positions 0 to 9 shown in FIG. 16at the operational time of the robot 13, respectively.

Several forces generated before the seal 10 comes into contact with theshaft 14 are averaged by the computer 33 (an average force 9: themaximum value or the minimum value mentioned below shows a valueobtained by subtracting the average force 9 from a measured value).Herein, the maximum value of the sliding-in force from the position 1 tothe position 3 shown in FIG. 16 is referred to as the maximum 1, theminimum value of the pulling-out force from the position 3 to theposition 4 shown in FIG. 16 is referred to as the minimum 1, and themaximum values and the minimum values in the sequentforward-and-backward movements are referred to as the maximum 2, themaximum 3, the maximum 4, the minimum 2, and the minimum 3,respectively.

(1) In the case where a judgment is made by either the sliding-in forceor the pulling-out force:

In the case where the absolute value of the minimum pulling-out force(the minimum 3) is larger than a predetermined value in the finalpulling-out operation, the curled lip 10A is judged not to be recovered.Sequently, even though the sliding-in operation is made, the curled lipis not in the least be recovered. In the case where the maximumsliding-in force (the maximum 4) is larger than a predetermined value inthe final sliding-in operation, the lip 10A is judged to be curled.

(2) In the case where a judgment is made by the proportion of thesliding-in force or the pulling-out force:

The proportion of the absolute value of the maximum sliding-in force(the maximum 1) in the first sliding-in operation and the absolute valueof the minimum pulling-out force (the minimum 3) in the finalpulling-out operation is calculated. In the case where the proportion ofthese absolute values is smaller than a predetermined value, the curledlip 10A is judged not to be recovered. Sequently, even though thesliding-in operation is made, the curled lip is not in the least berecovered. In the case where the proportion of the maximum sliding-inforce (the maximum 1) in the first sliding-in operation and the maximumsliding-in force (the maximum 4) in the final sliding-in operation iscalculated and this proportion is smaller than a predetermined value,the lip 10A is judged to be curled.

In (1) and (2) described above, in the case where the lip 10A is judgedto be curled, the computer 33 outputs a warning signal showing that thelip 10A is kept curled and sends it into the robot controller 34, andthereby the movement of the robot 13 is stopped and a warning sound ismade.

[Curled-Lip Judging Method 2]

When an unexpected noise come into the voltage signal outputted from theload cell 31, the voltage which is not the real voltage is inputted intothe computer 33. If this unreal voltage becomes the maximum value, theunreal voltage may be used in order to judge whether the lip 10A is keptcurled and thus an unprecise judgment may be made. In order to such anunprecise judgment, a curled-lip judgment shown in FIG. 18 is made.

In the same way as shown in FIG. 17, the axis of ordinates, and that ofabscissas, in a graph shown in FIG. 18 show the sliding-in force or thepulling-out force (Kgf), and time (seconds), respectively. Points 0 to 9shown in the wave transition graph correspond to the positions 0 to 9shown in FIG. 16, respectively.

Several forces generated before the seal 10 comes into contact with theshaft 14 are averaged by the computer 33 (an average force 9: thesliding-in force and the pulling-out force mentioned below shows a valueobtained by subtracting the average force 9 from a measured value). Theseal 10 comes into contact with the shaft 14 and the sliding-inoperation starts to be made, and then a certain period of time (acertain period of time A which is counted) passes from the time in theposition 1. The sliding-in force at this time is referred to as A. Also,a certain period of time (a certain period of time B which is counted)passes from the time in the position 3 where the pulling-out operationstarts to be made, and the pulling-out force at this time is referred toas B. In addition, certain periods of time C, E, and G pass from thetime in the positions where the sequent sliding-in operations start tobe made, and the sliding-in forces at the points of time is referred toas C, E, and G, respectively. Also, certain periods of time D and F passfrom the time in the positions where the sequent pulling-out operationsstart to be made, and the pulling-out forces at the points of time isreferred to as D and F, respectively.

(1) In the case where a judgment is made either by the sliding-in forceor by the pulling-out force:

In the case where the absolute value of the pulling-out force (thepulling-out force F) is larger than a predetermined value in the finalpulling-out operation, the curled lip 10A is judged not to be recovered.In the case where the sliding-in force (the sliding-in force G) islarger than a predetermined value in the final sliding-in operation, thelip 10A is judged to be curled.

(2) In the case where a judgment is made by the proportion of thesliding-in force or the pulling-out force:

The proportion of the absolute value of the sliding-in force (thesliding-in force A) in the first sliding-in operation and the absolutevalue of the pulling-out force (the pulling-out force G) in the finalpulling-out operation is calculated. In the case where the proportion ofthese absolute values is smaller than a predetermined value, the curledlip 10A is judged not to be recovered. In the case where the proportionof the sliding-in force (the sliding-in force A) in the first sliding-inoperation and the sliding-in force (the sliding-in force G) in the finalsliding-in operation is calculated and this proportion is smaller than apredetermined value, the lip 10A is judged to be curled.

In (1) and (2) described above, in the case where the lip 10A is judgedto be curled, the computer 33 outputs a warning signal showing that thelip 10A is kept curled and sends it into the robot controller 34, andthereby the movement of the robot 13 is stopped and a warning sound ismade.

[Curled-Lip Judging Method 3]

In FIG. 18, the sliding-in force or the pulling-out force at the pointof time when a certain period of time has passed is used in order tojudge whether the lip 10A is kept curled, and only one force of thesliding-in force and the pulling-out force is used. In other words, inorder to make a curled-lip judgment, only the sliding-in force A is usedin the first sliding-in operation, only the pulling-out force F is usedin the final pulling-out operation, and only the sliding-in force G isused in the final sliding-in operation. However, in the case where onlyone force of the sliding-in force and the pulling-out force is used inorder to make a curled-lip judgment, a precise curled-lip judgment maybe prevented from being made eaten with a slight noise coming in. Inorder to such an unprecise judgment, a curled-lip judgment shown in FIG.19 should be made.

In the same way as shown in FIG. 17 or FIG. 18, the axis of ordinates,and that of abscissas, in a graph shown in FIG. 19 show the sliding-inforce or the pulling-out force (Kgf), and time (seconds). respectively,According to this curled-lip judging method, the seal 10 comes intocontact with the shaft 14 and the sliding-in operation starts to bemade, and then a certain period of time (a counted period of time A)passes from the time in the position 1. Thereafter, the sliding-in forceis measured during a certain period of time (a counted period of timeA′). Also, after a certain period of time (a counted period of time B)has passed from the time in the position 3 where the pulling-outoperation starts to be made, the pulling-out force is measured during acertain period of time (a counted period of time B′). In the same way asmentioned above, after certain periods of time C, E, and G have passedfrom the time in the positions where the sliding-in operations start tobe made, the sliding-in forces are measured during counted periods oftime C′, E′, and G′, respectively. Also, after certain periods of time Dand F have passed from the time in the positions where the pulling-outoperations start to be made, the pulling-out forces are measured duringcounted periods of time D′ and F′, respectively.

Then, the average value (the average sliding-in force A′) of thesliding-in forces obtained in the measurement which has been taken aplurality of times during the counted period of time A′ is calculated.Similarly, the average values (the average pulling-out forces B′, D′,and F′) of the pulling-out forces obtained in the measurement which hasbeen taken a plurality of times during the counted periods of time B′,D′, and F′ are calculated. In the same way the average values (theaverage sliding-in forces C′, E′, and G′) of the sliding-in forcesobtained in the measurement which has been taken a plurality of timesduring the counted periods of time C′, E′, and G′ are calculated.

(1) In the case where a judgment is made either by the sliding-in forceor by the pulling-out force:

In the case where the absolute value of the average value (the averagepulling-out force F′) of the pulling-out force is larger than apredetermined value in the final pulling-out operation, the curled lip10A is judged not to be recovered. In the case where the average value(the average sliding-in force G′) of the sliding-in force (thesliding-in force G) is larger than a predetermined value in the finalsliding-in operation, the lip 10A is judged to be curled.

(2) In the case where a judgment is made by the proportion of thesliding-in force or the pulling-out force:

The proportion of the absolute value of the average value (the averagesliding-in force A′) of the sliding-in force in the first sliding-inoperation and the absolute value of the average value (the averagepulling-out force F′) of the pulling-out force in the final pulling-outoperation is calculated. In the case where the proportion of theseabsolute values is smaller than a predetermined value, the curled lip10A is judged not to be recovered. In the case where the proportion ofthe average value (the average sliding-in force A′) of the sliding-inforce in the first sliding-in operation and the average value (theaverage sliding-in force G′) of the sliding-in force in the finalsliding-in operation is calculated and this proportion is smaller than apredetermined value, the lip 10A is judged to be curled.

In (1) and (2) described above, in the case where the lip 10A is judgedto be curled, the computer 33 outputs a warning signal showing that thelip 10A is kept curled and sends it into the robot controller 34, andthereby the movement of the robot 13 is stopped and a warning sound ismade.

[Curled-Lip Judging Method 4]

In the case where the seal 10 is slid onto the shaft 14 with beingrotated, it can be judged whether the lip 10A is kept curled accordingto the sliding-in force detected in the sliding-in operation.

FIG. 20 shows the variation in the sliding-in force detected when theseal 10 is slid onto the shaft 14. Before the seal 10 comes into contactwith the shaft 14, that is, when the seal 10 is in a position (1),several forces are averaged by the computer 33 (an average force a: thesliding-in force mentioned below shows a value obtained by subtractingthe average force a from a measured value). In FIG. 20, referencecharacter (2) designates a position at the exact time when the seal 10has been slid onto the shaft 14, (3) designates a position in which theseal 10 starts to be rotated and slid, (4) designates a position inwhich the seal 10 stops being rotated and completes its sliding-in. Theseal 10 is rotated and slid in the region from (3) to (4).

The sliding-in force is detected, naturally, in theseal-rotating-and-sliding region from (3) to (4), however, it is usuallydetected in a region (5) where the output wave transition of thesliding-in force becomes stable. If the detected sliding-in force b islarger than a predetermined value, the lip 10A is judged to be keptcurled. In this case, if any noises come into the system during theperiod of time when a judgment is made only by the detected sliding-inforce b, a precise judgment may be prevented from being made. In orderto such an unprecise judgment, it is desirable that the sliding-in forceis detected a plurality of times in the region, (5) and that it isjudged whether the lip 10A is kept curled according to the average valuecalculated from these detected values of the sliding-in force.

In FIG. 20, the seal 10 is rotated. However, the shaft 14 may also berotated without any rotation of the seal 10, or both of the seal 10 andthe shaft 14 may also be rotated. In the case where both of the seal 10and the shaft 14 are rotated, preferably, the seal 10 should be rotatedin the reverse direction to a rotational direction of the shaft 14.

[Curled-Lip Judging Method 5]

The time taken when the seal 10 is slid onto the shaft 14 varies withthe work. Therefore, the period of time A which is counted from theposition 1, which is shown in FIG. 18 or FIG. 19, may also vary with thework.

According to this curled-lip judging method, the sliding-in force in thefirst operation where the seal 10 is once slid onto the shaft 14 ismeasured point by point, the wave transitional line of the sliding-inforce is obtained from the measured result. Since the seal 10 comes intocontact with the shaft 14 when the seal 10 moves from the position 0 tothe position 1, as shown in FIG. 18 or FIG. 19, the amplitude of thewave of the sliding-in force in the first operation varies largely andthus the wave transitional line becomes into a conspicuous transientstate. Continuously, when the seal 10 moves from the position 1 to theposition 2 in the sliding-in operation, the lip 10A comes into contactwith the step portion (an inclined surface 14D) between the D-cutportion 14C and the shaft body 14B. At this time, also the amplitudeoscillates to some extent. and a transient state of the wave isobserved. In addition, a part of the lip 10A is curled. Sequently, whenthe seal 10 has reached the position 3 in the sliding-in operation, thesliding-in operation is shifted to the pulling-out operation, andthereby the value on the wave transitional line of the sliding-in forceshifts from the area of positive values to that of negative values.Hence, when the seal 10 has reached the position 3, the lip 10A is keptcurled over its whole circumference.

According to the usual wave transition of the sliding-in force mentionedabove, the transient state on the wave transitional line of thesliding-in force is observed, and thereby the relative position betweenthe shaft 14 and the seal 10 can be estimated. Then, the sliding-inforce in the estimated position is detected. If the value obtained fromthe detected result is larger than a predetermined value, the lip 10Acan be judged to be kept curled. According to the aforementioned method,errors in measurement in each work become less, so that a precisecurled-lip judgment can be made.

The predetermined value which is used for judging the sliding-in forceby comparison is determined according to data obtained in experiments.However, measured data of some works may be out of the range includingdata obtained in experiments, and in this case, a precise judgmentcannot be made.

Therefore, according to this curled-lip judging method, the sliding-inforce in a position estimated from the wave transitional line of thesliding-in force is used for preliminarily judging whether thecurled-lip judgment can be made. According to this method, thesliding-in force which is out of the data range obtained in experimentsis eliminated from objective data for the judgment, so that the accuracyof the curled-lip judgment can be made higher.

FIG. 21 is a flow chart showing this curled-lip judging method. In FIG.21, steps 100 and 101 show processes comprised by this curled-lipjudging method, and steps 102 and 103 show processes comprised by theaforementioned curled-lip judging method 1, 2, or 3, respectively.

When the seal 10 is slid onto the shaft 14, even the end of the lip 10Amay be curled. In order to resolve this problem, as shown in FIG. 14, ataper portion 14E is formed in the end part of the shaft 14, and adiameter d1 of the end surface of the taper portion 14E is designed tobe smaller than an inner diameter d2 (see FIG. 16) of the lip 10A of theseal 10. According to such a construction, even though the lip 10A hascome into contact with the taper portion 14E while the seal 10 is slidonto the shaft 14, the lip 10A can be prevented from being curled.

Further, in order to prevent the lip 10A from being curled while theseal 10 is moving near the D-cut portion 14C (in the region between theposition 1 and the position 2 shown in FIG. 16), it is necessary thatthe relation between a length d3 in the diametrical direction of theshaft 14 in the D-cut portion 14C (a segment of a line including thelength d3 is perpendicular to the plane part of the D-cut portion 14Cand is the minimum diameter), and the inner diameter d2 of the lip 10Aof the seal 10, is designed to become as shown below.

d 3 ≦d 2

Next, there will be explained a method for recovering the curled lipinto the initial state, by which the lip 10A is recovered even thoughthe lip 10A has been curled.

[Method of Using the D-Cut Portion]

In the case where the D-cut portion 14C is formed in the shaft 14, asshown in FIG. 22, when the seal 10 is positioned on the D-cut portion14C, the curled lip 10A is recovered with the difference in step betweenthe shaft body 14B and the D-cut portion 14C. In FIG. 22, referencecharacter 10A′ designates a portion in which the curled lip 10A has beenrecovered, and 10A″ designates a portion in which the curled lip 10A hasnot been recovered.

In the D-cut portion 14C, as described above, the length d3 in thediametrical direction is designed to be shorter than the inner diameterd2 of the lip 10A. FIGS. 23(A) and 23(B) show the shaft 14 having theD-cut portion 14C. FIG. 23(A) is a front view of the shaft 14, and FIG.23(B) is a sectional view of the shaft 14, cut along a B—B line in theD-cut portion 14C.

As shown in FIG. 22, when the shaft 14 is rotated while the seal 10 ison the D-cut portion 14C, the curled lip 10A starts to be recovered withthe rotation of the D-cut portion 14C and is recovered over the entirecircumference at the time when the shaft 14 has made substantially onerotation. In order to ensure the recovery of the curled lip, desirably,the shaft 14 is rotated once or more times. Herein, the shaft 14 may berotated in a state where the seal 10 does not move or does move (i.e.,slide in and pull out) in the direction of the axial line of the shaft14. After the curled lip has been recovered, the seal 10 is moved to thepredetermined position of the shaft body 14B. Thereby, the seal 10 canbe slid onto the shaft 14 without being curled over the entirecircumference of the shaft 14.

In the case where the step portion is formed between the D-cut portion14C and the shaft body 14B, when the seal 10 which has recovered fromthe state where the lip is kept curled moves from the D-cut portion 14Cto the shaft body 14B, the lip 10A may be hooked and curled again by thestep portion. In order to prevent the lip 10A from being curled again,the shaft 14 is rotated while the seal 10 is moving. Further, as shownin FIGS. 14 to 16, in the case where the inclined surface 14D is formedin the step portion between the shaft body 14B and the D-cut portion14C, when the seal 10 is slid in from the D-cut portion 14C to the shaftbody 14B, the lip 10A can be prevented from being hooked and curled bythe step portion.

In order to recover the curled lip 10A to the initial state, instead ofthe D-cut portion 14C, a cut portion shown in each of FIGS. 24(A), 24(B)to 28(A), 28(B) may also be formed in one end part of the shaft 14. InFIGS. 24(A), 24(B) to 28(A), 28(B), (A) is a front view of the shaft 14,and (B) is a sectional view of the shaft 14 in the same position as theposition shown in FIGS. 23(A) and 23(B), respectively.

While the D-cut portion 14C shown in FIGS. 23(A) and 23(B) has a flatcut surface, that in FIGS. 24(A) and 24(B) has a cylindrical convex cutsurface, that in FIGS. 25(A) and 25(B) has a cylindrical concave cutsurface, and that in FIGS. 26(A) and 26(B) has a groove-like cutsurface. In FIGS. 27(A) and 27(B), flat cut surfaces are formed on bothsides of the shaft 14, and in FIGS. 28(A) and 28(B), cylindrical convexcut surfaces (an elliptic shape in its sectional view) are formed onboth sides of the shaft 14.

In FIGS. 22 to 28(A), 28(B), the D-cut portion 14C is formed in one endpart of the shaft, however, as shown in FIG. 29, in order to recover thecurled seal 10, a D-cut portion 14C′ may also be formed in a certainpart of the shaft 14 so that the shaft 14 is rotated after the seal 10has been positioned on the D-cut portion 14C′. Herein, the part of theD-cut portion 14C′ may also be shaped as shown in FIGS. 24(A), 24(B) to28(A), 28(B).

In FIG. 29, reference character R1 designates a region of the D-cutportion 14C′ of the shaft 14, R2 designates a cylindrical region of theshaft 14 in the direction of the front end of the lip 10A (in thedirection toward which the seal 10 is slid in), and R3 designates acylindrical region of the shaft 14 in the direction of the back end ofthe lip 10A (in the direction from which the seal 10 is slid in). Theshaft 14 is rotated in the region R1, so that the seal 10 can berecovered from its curled state. Next, when the seal 10 is moved (isslid in more) toward the region R2, in the same way as shown in FIG. 22,the lip 10A may be curled again in the boundary between the region R1and the region R2 because of a step portion. In this case, also, inorder to prevent the lip 10A from being curled again, the shaft 14 isrotated while the seal 10 is moving.

In FIG. 22 and FIG. 29, only the shaft 14 is designed to be rotated atthe time when the seal 10 is on the D-cut portion 14C or 14C′. However,only the seal 10 may also be rotated without any rotation of the shaft14, or both of the shaft 14 and the seal 10 may also be rotated.

The aforementioned seal-sliding apparatus in FIG. 1 or FIG. 2 is used inorder to rotate only the shaft 14, the aforementioned seal-slidingapparatus in FIG. 3 is used in order to rotate only the seal 10, and theaforementioned seal-sliding apparatus in FIG. 4 is used in order torotate both of the shaft 14 and the seal 10. In the case where both ofthe shaft 14 and the seal 10 are rotated, preferably, preferably, theshaft 14 should be rotated in the reverse direction to a rotationaldirection of the seal 10.

[Method of Using the Circumferential Groove]

FIG. 30 shows a method for returning the curled lip into the initialstate with a circumferential groove 14F formed in the outer surface ofthe shaft 14. A width w1 of the circumferential groove 14F is largerthan a height w2 by which the lip 10A projects, and an outer diameter d4of the bottom part of the circumferential groove 14F is smaller than aninner diameter d2 of the lip 10A.

In the case where the circumferential groove 14F is formed, when theseal 10 is positioned on the circumferential groove 14F, the curled lip10A is recovered to the initial state at the circumferential groove 14F.When it is recovered even though the seal 10 is positioned on thecircumferential groove 14F, the shaft 14 is rotated relatively to theseal 10 in order to ensure that the curled lip 10A is recovered.

Herein, the section (the plane perpendicular to the central axis) of theshaft 14 at the circumferential groove 14F has a circular shape.However, as long as the circumferential groove 14F has an enough depthto recover the curled lip 10A, the section mentioned above may also haveanother shape such as an elliptic shape.

[Method of Using the Jig Member]

FIG. 31 shows a method for returning the curled lip into the initialstate with a jig member 60 which is connected to the end surface of theshaft 14 in the case where the shaft 14 does not have a D-cut portion ora circumferential groove. A D-cut portion 60A is formed on one side ofthe jig member 60, and the jig member 60 is combined with the shaft 14so as to correspond to the central axis of the shaft 14. When lip 10Ahas been curled, the seal 10 is brought to the D-cut portion 60A and thejig member 60 is rotated relatively to the seal 10, so that the curledlip 10A can be recovered. Herein, the jig member 60 or the seal 10 needsto be rotated once or more times.

As shown in FIG. 32, in the jig member 60, a length d5 in thediametrical direction at the D-cut portion 60A is designed to be shorterthan the inner diameter d2 of the lip 10A.

FIGS. 33(A) to (D) show some methods for combining the jig member 60with the shaft 14. According to a method shown in FIG. 33(A), asquare-pillar-shaped shaft 60B is disposed at the end surface of the jigmember 60, and the square-pillar-shaped shaft 60B is engaged with asquare-pillar-shaped hole 14G formed in the end of the shaft 14 so thatthe jig member 60 is combined with the shaft 14. According to a methodshown in FIG. 33(B), a cylindrical shaft 60C is disposed at the endsurface of the jig member 60, and the cylindrical shaft 60C is engagedwith a cylindrical hole 14H formed in the end of the shaft 14 so thatthe jig member 60 is combined with the shaft 14.

In the case shown in FIG. 33(A), since a square-pillar-shaped portionsuch as the square-pillar-shaped shaft 60B is engaged with asquare-pillar-shaped portion such as the square-pillar-shaped hole 14G,when the shaft 14 is rotated, the rotating force can be securelytransmitted to the jig member 60. On the other hand, since a cylindricalportion such as the cylindrical shaft 60C is engaged with a cylindricalportion such as the cylindrical hole 14H, a slip may occur between thecylindrical shaft 60C and the cylindrical hole 14H. Thereby, therotating force of the shaft 14 may not be securely transmitted to thejig member 60. In such a case, if the shaft 14 is made of, for example,a magnetic material such as iron or the like, as shown in FIG. 33(C), amagnet 60D is attached to the end part of the jig member 60, so that theshaft 14 can be prevented from slipping on the jig member 60. Further,as shown in FIG. 33(D), any special constructions other than theconstruction where the magnet 60D is attached to the end part of the jigmember 60 are not required. Such a method is preferably used in the casewhere the end part of the shaft 14 or the jig member 60 cannot beprocessed.

Further, if the jig member 60 is made of, for example, a magneticmaterial such as iron or the like, a magnet can also be attached to theend part of the shaft 14. Further, a magnet may also be attached to eachend part of the shaft 14 and the jig member 60.

Further, instead of the D-cut portion 14C, a cut portion having a shapeshown in each of FIGS. 34(A), 34(B) to 38(A), 38(B), can be formed inone end part of the jig member 60. In FIGS. 34(A), 34(B) to 38(A),38(B), (A) is a front view of the jig member 60, and (B) is a sectionalview of the jig member 60 at the cut portion. While the D-cut portion14C has a flat cut surface, that in FIGS. 34(A) and 34(B) has acylindrical convex cut surface, that in FIGS. 35(A) and 35(B) has acylindrical concave cut surface, and that in FIGS. 36(A) and 36(B) has agroove-like cut surface. In FIGS. 37(A) and 37(B), flat cut surfaces areformed on both sides of the jig member 60, and In FIGS. 38(A) and 38(B),cylindrical convex cut surfaces (an elliptic shape in its sectionalview) are formed on both sides of the shaft 14.

Further, the D-cut portion 60A or the cut portion shown in each of FIGS.34(A), 34(B) to 38(A), 38(B), can also be formed in the middle part inthe longitudinal direction of the jig member 60.

In the case where there is a step portion between the circular part (thepart close to the shaft 14) of the jig member 60 and the cut portion(e.g., the D-cut portion 60A), when the seal recovered from the curledstate moves from the jig member 60 toward the shaft 14, the lip 10A maybe hooked and curled again by the step portion. Therefore, in this case,the jig member 60 is rotated relatively to the seal 10, and thus the lip10A can be prevented from being curled again. Further, as shown in FIG.39, if an inclined surface 60G is formed in the step portion between acircular part 60E of the jig member 60 and a cut portion 60F, the lip10A can be prevented from being hooked and curled by the step portion.

Further, a jig member 61 shown in FIG. 40 can also be used in order torecover the curled seal 10. A small-diameter portion 61A is formed atthe end surface of the jig member 61. The small-diameter portion 61A isconnected to the end surface of the shaft 14, whose construction isequivalent to the circumferential groove 14F shown in FIG. 30. Accordingto the construction shown in FIG. 40, therefore, the curled seal 10 canbe recovered at the circumferential groove.

Herein, a length w3 by which the small-diameter portion 61A projects islonger than the height w2 of the lip 10A, and in addition, an outerdiameter d6 of the small-diameter portion 61A is shorter than the innerdiameter d2 of the lip 10A. Further, the small-diameter portion 61A canbe formed in the middle part in the longitudinal direction of the jigmember 61 as well as at the end of the jig member 61.

What is claimed is:
 1. A seal-sliding apparatus for sliding a seal witha lip onto a shaft, comprising: holding means for holding said sealdetachably in a direction of an axial line of said shaft; andshaft-rotating means for rotating said shaft; wherein said seal is slidonto said shaft while said shaft is rotated around the axial line bysaid shaft-rotating means.
 2. A seal-sliding apparatus according toclaim 1, wherein said shaft-rotating means rotates said shaft in onedirection.
 3. A seal-sliding apparatus according to claim 1 wherein saidshaft-rotating means rotates said shaft alternately in one direction andin a direction opposite to said one direction.
 4. A seal-slidingapparatus for sliding a seal with a lip onto a shaft, comprising:holding means for holding said seal detachably in a direction of anaxial line of said shaft; and seal-rotating means for rotating said sealheld by said holding means; wherein said seal is slid onto said shaftwhile said seal is rotated around the axial line of said shaft by saidseal-rotating means.
 5. A seal-sliding apparatus according to claim 4,wherein said seal-rotating means rotates said seal in one direction. 6.A seal-sliding apparatus according to claim 4, wherein saidseal-rotating means rotates said seal alternately in one direction andin a direction opposite to said one direction.
 7. A seal-slidingapparatus for sliding a seal with a lip onto a shaft, comprising:holding means for holding said seal detachably in a direction of anaxial line of said shaft; seal-rotating means for rotating said sealheld by said holding means; and shaft-rotating means for rotating saidshaft; wherein said seal is slid onto said shaft while said seal isrotated by said seal-rotating means and while said shaft is rotated bysaid shaft-rotating means.
 8. A seal-sliding apparatus according toclaim 7, wherein said shaft-rotating means rotates said shaft in onedirection, and said seal-rotating means rotates said seal in a directionopposite to said one direction of said shaft.
 9. A seal-slidingapparatus according to claim 7, wherein said shaft-rotating meansrotates said shaft alternately in one direction and in a directionopposite to said one direction, and said seal-rotating means rotatessaid seal in a direction opposite to the rotational direction of saidshaft.
 10. An apparatus for inserting a seal onto a shaft, said sealincluding an opening formed in a substantially same shape as an outerperiphery of said shaft and contacting to said shaft, said seal furtherincluding a front end which contacts to said shaft and is formed to bethin along an axial direction of said shaft, said apparatus comprising:holding means for holding said seal and sliding said seal onto saidshaft; and controlling means for controlling said holding means so thata first operation is performed in which said seal is slid onto saidshaft, thereafter a second operation is performed in which said seal ispulled out to a position where said seal does not slip off from saidshaft, and thereafter a third operation is performed in which said sealis inserted again onto said shaft, the second and third operations beingperformed once or a plurality of times; wherein said controlling meanscontrols a first speed at which said seal is slid onto said shaft insaid first operation, a second speed at which said seal is pulled out insaid second operation, and a third speed at which said seal is insertedagain onto said shaft in said third operation so that the first, second,and third speeds differ from each other, and the speed at which saidseal is pulled out in said second operation is lower than the speed atwhich said seal is inserted in said third operation.
 11. An apparatusaccording to claim 10, wherein said controlling means controls said sealto be slid onto said shaft while rotating said shaft in said thirdoperation.
 12. An apparatus for inserting a seal onto a shaft, said sealincluding an opening formed in a substantially same shape as an outerperiphery of said shaft and contacting to said shaft, said seal furtherincluding a front end which contacts to said shaft and is formed to bethin along an axial direction of said shaft, said apparatus comprising:holding means for holding said seal and sliding said seal onto saidshaft; and controlling means for controlling said holding means so thata first operation is performed in which said seal is slid onto saidshaft, thereafter a second operation is performed in which said seal ispulled out to a position where said seal does not slip off from saidshaft, and thereafter a third operation is performed in which said sealis inserted again onto said shaft, the second and third operations beingperformed once or a plurality of times; wherein said controlling meanscontrols a first speed at which said seal is slid onto said shaft insaid first operation, a second speed at which said seal is pulled out insaid second operation, and a third speed at which said seal is insertedagain onto said shaft in said third operation so that the first, second,and third speeds differ from each other, and the speed at which saidseal is inserted in said third operation is higher than the speed atwhich said seal is slid in said first operation.
 13. An apparatusaccording to claim 12, wherein said shaft comprises a cylindricalportion and a non-cylindrical portion, and said controlling meanscontrols the second and third operations to be performed at saidcylindrical portion of said shaft.
 14. An apparatus according to claim12, wherein said shaft comprises a cylindrical portion and anon-cylindrical portion, and said controlling means controls the secondand third operations to be performed at said cylindrical portion of saidshaft.
 15. An apparatus according to claim 12, wherein said controllingmeans controls said seal to be slid onto said shaft while rotating saidshaft in said third operation.
 16. An apparatus for inserting a sealonto a shaft, said seal including an opening formed in a substantiallysame shape as an outer periphery of said shaft and contacting to saidshaft, said seal further including a front end, which contacts to saidshaft, being formed to be thin along an axial direction of said shaft,said apparatus comprising: first means for curling at least a part ofsaid front end when said seal is slid onto said shaft; second means forstraightening a curl of said front end formed by said first means insuch a way that said seal is positioned at a cut portion formed in anouter circumferential surface of said shaft and, at the same time, saidshaft and said seal are rotated relatively with each other; and thirdmeans for situating said seal said front end of which has been uncurledat a predetermined position.
 17. An apparatus according to claim 16,wherein a minimum diameter of said shaft at said cut portion is smallerthan an inner diameter of said front end.
 18. An apparatus according toclaim 16, wherein said second means rotates said inserting means.
 19. Anapparatus according to claim 16, wherein said second means rotates saidseal.
 20. An apparatus according to claim 16, wherein said second meansrotates both said shaft and said seal.
 21. An apparatus according toclaim 20, wherein said second means rotates said shaft and said seal inopposite directions with respect to each other.
 22. An apparatusaccording to claim 16, wherein said cut portion has a flat cut surface.23. An apparatus according to claim 16, wherein said cut portion has acylindrical convex cut surface.
 24. An apparatus according to claim 16,wherein said cut portion has a cylindrical concave cut surface.
 25. Anapparatus according to claim 16, wherein said cut portion has agroove-like cut surface.
 26. An apparatus according to claim 16, whereinsaid cut portion is formed on one side of said shaft, and another cutportion is formed on the other side of said shaft with a central axis ofsaid shaft between them.
 27. An apparatus according to claim 16, whereinan inclined surface is formed in a step portion between the outercircumferential surface of said shaft and said cut portion, and saidthird means moves said seal whose front end has been uncurled from saidcut portion to a predetermined position by utilizing said inclinedsurface.
 28. A seal-sliding apparatus for positioning a seal with a liponto a shaft having a circumferential groove formed in an outer surfacethereof, comprising: means for positioning said seal at thecircumferential groove of said shaft in order to uncurl said lip of saidseal to an initial sealing shape; and lip uncurling means for rotatingat least one of said seal and said shaft in order to ensure that saidlip is uncurled to the initial sealing shape.
 29. A seal-slidingapparatus according to claim 28, wherein a minimum diameter of saidshaft at said circumferential groove is smaller than an inner diameterof said lip, and a width of said circumferential groove is larger than aprojecting height of said lip.
 30. A seal-sliding apparatus according toclaim 28, wherein said lip uncurling means rotates said shaft and saidseal relatively with each other when said seal is at saidcircumferential groove.
 31. A seal-sliding apparatus according to claim30, wherein said lip uncurling means rotates said shaft and said seal inopposite directions with respect to each other.
 32. A seal-slidingapparatus for positioning a seal with a lip onto a shaft, comprising: ajig member combined coaxially to a central axis of said shaft and havinga cut portion formed in an outer circumferential surface thereof; andlip uncurling means for positioning said seal adjacent to said cutportion of said jig and for rotating said jig member and said sealrelatively with each other in order to ensure that said lip of said sealis uncurled to an initial sealing shape.
 33. A seal-sliding apparatusaccording to claim 32, wherein a minimum diameter of said jig member atsaid cut portion is smaller than an inner diameter of said lip.
 34. Aseal-sliding apparatus according to claim 32, wherein said lip uncurlingmeans rotates said jig member.
 35. A seal-sliding apparatus according toclaim 32, wherein said lip uncurling means rotates said seal.
 36. Aseal-sliding apparatus according to claim 32, wherein said lip uncurlingmeans rotates both said jig member and said seal.
 37. A seal-slidingapparatus according to claim 36, wherein said lip uncurling meansrotates said jig member and said seal in opposite directions withrespect to each other.
 38. A seal-sliding apparatus according to claim32, wherein said cut portion of said jig member has a flat cut surface.39. A seal-sliding apparatus according to claim 32, wherein said cutportion of said jig member has a cylindrical convex cut surface.
 40. Aseal-sliding apparatus according to claim 32, wherein said cut portionof said jig member has a cylindrical concave cut surface.
 41. Aseal-sliding apparatus according to claim 32, wherein said cut portionof said jig member has a groove-like cut surface.
 42. A seal-slidingapparatus according to one of claims 38 to 41, wherein said cut portionis formed on both sides of said jig member with a central axis of saidjig member therebetween.
 43. A seal-sliding apparatus according, to oneof claims 38 to 41, wherein an inclined surface is formed in a stepportion between an outer circumferential surface and the cut surface ofsaid jig member.
 44. A seal-sliding apparatus for positioning a sealwith a lip onto a shaft, comprising: a jig member combined coaxially toa central axis of said shaft and having a circumferential groove formedin an outer circumferential surface thereof; and lip uncurling means forpositioning said seal adjacent to said circumferential groove of saidjig and for rotating said jig member and said seal relatively with eachother in order to ensure that said lip of said seal is uncurled to aninitial sealing shape.
 45. A seal-sliding apparatus according to claim44, wherein a minimum diameter of said jig member at saidcircumferential groove is smaller than an inner diameter of said lip,and a width of said circumferential groove is larger than a projectingheight of said lip.
 46. A seal-sliding apparatus according to claim 44,wherein said lip uncurling means rotates said jig member and said sealrelatively with each other when said seal is at said circumferentialgroove.
 47. A seal-sliding apparatus according to claim 46, wherein saidlip uncurling means rotates said jig member.
 48. A seal-slidingapparatus according to claim 46, wherein said lip uncurling meansrotates said seal.
 49. A seal-sliding apparatus according to claim 46,wherein said lip uncurling means rotates both said jig member and saidseal.
 50. A seal-sliding apparatus according to claim 49, wherein saidlip uncurling means rotates said jig member and said in oppositedirections with respect to each other.
 51. A seal-sliding apparatusaccording to claim 32 to 44, wherein said jig member is removed fromsaid shaft after a lip uncurling operation is completed.